The invention relates to novel methods, compositions, and apparatuses for improving the effectiveness of froth flotation beneficiation processes. In a beneficiation process, two or more materials which coexist in a mixture (the fines) are separated from each other using chemical and/or mechanical processes. Often one of the materials (the beneficiary) is more valuable or desired than the other material (the gangue).
As described for example in U.S. Pat. Nos. 4,756,823, 5,304,317, 5,379,902, 7,553,984, 6,827,220, 8,093,303, 8,123,042, and in Published US Patent Applications 2010/0181520 A1 and 2011/0198296, one form Ff beneficiation is froth flotation separation. In froth flotation separation the fines are mixed with water to form slurry. The slurry is then sparged to form bubbles which rise up out of the slurry. The more hydrophobic material (the concentrate) adheres to and rises up with the bubbles and gathers in a froth layer above the slurry. The froth layer is then is deposited on a launder where the concentrate gathers. The less hydrophobic material (the tailings) remains behind in the slurry.
Two common forms of flotation separation processes are direct flotation and reverse flotation. In direct flotation processes, the concentrate is the beneficiary and the tailings are the gangue. In reverse flotation processes, the gangue constituent is floated into the concentrate and the beneficiary remains behind in the slurry. The object of the all flotation is to separate and recover as much of the valuable constituent(s) of the fine as possible in as high a concentration as possible which is then made available for further downstream processing steps.
Froth flotation separation can be used to separate solids from solids (such as the constituents of mine ore) or liquids from solids or from other liquids (such as the separation of bitumen from oil sands). When used on solids, froth separation also includes having the solids comminuted (ground up by such techniques as dry-grinding, wet-grinding, and the like). After the solids have been comminuted they are more readily dispersed in the slurry and the small solid hydrophobic particles can more readily adhere to the sparge bubbles.
There are a number of additives that can be added to increase the efficiency of a froth flotation separation. Collectors are additives which adhere to the surface of concentrate particles and enhance their overall hydrophobicity. Gas bubbles then preferentially adhere to the hydrophobicized concentrate and it is more readily removed from the slurry than are other constituents, which are less hydrophobic or are hydrophilic. As a result, the collector efficiently pulls particular constituents out of the slurry while the remaining tailings which are not modified by the collector, remain in the slurry. This process can also or instead utilize chemicals, which increase the hydrophilic properties of materials selected to remain within the slurry. Examples of collectors include oily products such as fuel oil, tar oil, animal oil, vegetable oil, fatty acids, fatty amines, and hydrophobic polymers. Other additives include frothing agents, regulators, depressors (deactivators) and/or activators, which enhance the selectivity of the flotation step and facilitate the removal of the concentrate from the slurry.
Because collectors adhere to the surfaces of concentrate particles, their effectiveness is dependent on the nature of the interactions that occur between the collectors and the concentrate particles. Unfortunately contradictory principles of chemistry are at work in froth flotation separation which forces difficulties on such interactions. Because froth flotation separation relies on separation between more hydrophobic and more hydrophilic particles, the slurry medium often includes water. Because however many commonly used collectors are themselves hydrophobic, they do not disperse well in water which makes their interactions with concentrate particles difficult or less than optimal.
One method that has been used to better disperse water immiscible collectors in slurry is through the use of chemical agents such as emulsifiers to disperse the collector in the slurry as an oil-in water type emulsion. Unfortunately here too contradictory chemistry has hampered this attempt. To make oil-in-water emulsions stable sufficient amounts of emulsifiers have to be used to cover the surface of oil droplets with a hydrophobic tail portion and the water phase with a hydrophilic group. However, when used in these amounts emulsifiers reduce the hydrophobicity of the collector thus defeating the entire purpose of being a collector. As a result water immiscible collector performance remains degraded because of either poor dispersing or because of impaired hydrophobicity. In addition using sufficient emulsifiers to disperse collectors often causes interferes with other additives (frothing agents in particular).
Thus it is clear that there is definite utility in improved methods, compositions, and apparatuses for dispersing collectors in froth separation slurry. The art described in this section is not intended to constitute an admission that any patent, publication or other information referred to herein is “prior art” with respect to this invention, unless specifically designated as such. In addition, this section should not be construed to mean that a search has been made or that no other pertinent information as defined in 37 CFR §1.56(a) exists.